Fabrication of electronic circuit elements using liquid deposition techniques is of profound interest as such techniques provide potentially low-cost alternatives to conventional mainstream amorphous silicon technologies for electronic applications such as thin film transistors (TFTs), light-emitting diodes (LEDs), RFID tags, photovoltaics, and the like. However, the deposition and/or patterning of functional electrodes, pixel pads, and conductive traces, lines and tracks, which meet the conductivity, processing, and cost requirements for practical applications, have been a great challenge.
Solution-processable conductors are of great interest for use in such electronic applications. Metal nanoparticle-based inks represent a promising class of materials for printed electronics. However, most metal nanoparticles, such as silver and gold metal nanoparticles, require large molecular weight stabilizers to ensure proper solubility and stability in solution. These large molecular weight stabilizers inevitably raise the annealing temperatures of the metal nanoparticles above 200° C. in order to burn off the stabilizers, which temperatures are incompatible with most low-cost plastic substrates such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) that the solution may be coated onto and can cause damage thereto.
Furthermore, current metal nanoparticle compositions when deposited on a substrate often result in conductive metal ink lines that are too wide, exhibit a low conductivity and have a “coffee ring effect”. “Coffee ring effect” is referred to herein as the widening of a deposited metal ink line such that it displays a bimodal line profile (two peaks) in a surface profile measurement. The deposition of a conductive metal ink lines that exhibit a coffee ring effect and/or are otherwise too wide may limit their use in certain applications.